//  Utils.java
//
//  Author:
//       Antonio J. Nebro <antonio@lcc.uma.es>
//       Juan J. Durillo <durillo@lcc.uma.es>
//
//  Copyright (c) 2011 Antonio J. Nebro, Juan J. Durillo
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU Lesser General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU Lesser General Public License for more details.
// 
//  You should have received a copy of the GNU Lesser General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
package jmetal.metaheuristics.moead;

/**
 * Utilities methods to used by MOEA/D
 */
public class Utils {

    public static double distVector(double[] vector1, double[] vector2) {
        int dim = vector1.length;
        double sum = 0;
        for (int n = 0; n < dim; n++) {
            sum += (vector1[n] - vector2[n]) * (vector1[n] - vector2[n]);
        }
        return Math.sqrt(sum);
    } // distVector

    public static void minFastSort(double x[], int idx[], int populacaoTamanho_, int T_) {
        for (int i = 0; i < T_; i++) {
            for (int j = i + 1; j < populacaoTamanho_; j++) {
                if (x[i] > x[j]) {
                    double temp = x[i];
                    x[i] = x[j];
                    x[j] = temp;
                    int id = idx[i];
                    idx[i] = idx[j];
                    idx[j] = id;
                } // if
            }
        } // for

    } // minFastSort

/**
 * Step 3
 * Step 3.1 Selection of Mating/Update Range
 */
    public static void randomPermutation(int[] perm, int size) {
        int[] index = new int[size];
        boolean[] flag = new boolean[size];

        for (int n = 0; n < size; n++) {
            index[n] = n;
            flag[n] = true;
        }

        int num = 0;
        while (num < size) {
            int start = jmetal.util.PseudoRandom.randInt(0, size - 1);
            //int start = int(size*nd_uni(&rnd_uni_init));
            while (true) {
                if (flag[start]) {
                    perm[num] = index[start];
                    flag[start] = false;
                    num++;
                    break;
                }
                if (start == (size - 1)) {
                    start = 0;
                } else {
                    start++;
                }
            }
        } // while
    } // randomPermutation
}
